With regard to judicial review of an agency's construction [dt: Auslegung] of the statute which it administers, if Congress has not directly spoken to the precise question at issue, the question for the court is whether the agency's answer is based on a permissible construction of the statute.

Chevron requires a federal court to defer to an agency’s construction, even if it differs from what the court believes to be the best interpretation, if the particular statute is within the agency’s jurisdiction to administer, the statute is ambiguous on the point at issue, and the agency’s construction is reasonable.